Mandrel positioning and ram arresting apparatus



July 28 1959 c. G. A. swANsoN 2,896,783

MANDREL POSITIONING AND RAM'ARRESTING APPARATUS e sheets-sheet 1 Filed July 6. 1954 bw N N QN n SRWN im?, QQ N NQ.. .THU ,riUwHmlwWJm/m a. w ...m mwa I: I.. h uw Q SWW INVENTOR.

@ya JJM uw nu A Z Top/vifs July v28, 1.959 c. G. A. swANsoN MANDREL PosITIoNING Ao RAM ARRESTING APPARATUS Filed July e. 1954 6 Sheets-Sheet 2 INVENToR. Jwmm I @nu MIM ATroQ/VEYLS `C. G. A. SWANSON July 28, 1959 MANDREI.. POSITIONING AND RAM ARRESTING APPARATUS Y Filed July e. A1954 6 Sheets-Sheet 5 NVENTolL y BY @ML JM AT Top/TVS July 2s, 1959 C. G. A. SWANSON MANDREL POSI'I'IONIIlG- AND RAM ARRESTING APPARATUS 6 Sheets-Sheet 4 Filed July e. 1954 Tok.

ATTORNEYS July 28, 1959 c. G. A. vs-zwANsoN 2,896,783

MANDREL POSITIONING AND RAM ARRESTING APPARATUS Filed July 6. `1954 6 Sheets-Sheet 5 'Ca/eg QJ INVENTOR.

'A TToPM/FYS July 28', 1959 c. G. A. swANsoN 2,896,783

MANDREL POSITIONING AND RAM ',ARRESTING APPARATUS Filed July e.. 1954 y s sheets-shears v \D o I *0. 2 s

Ba "L JNVENTOR.

* @MXN ,4-Topnews' United States ,Patent Office MANDREL POSITIONNG AND RAM lARRES'HNG APPARATUS Carl G. zA. Swanson, Kenmore, N.Y., assignor, -hy mesne assignments, to Lake Erie Machinery Corporation, Buffalo, N.Y., a corporation of New York cApplication `Iuly 6, 1954, 'Serial No. 441,225 6 Claims. (cl. 207-31 This invention relates to an extrusion press and more particularly to a hydraulic press for extruding relatively small internal diameter tubing from hot hollow or pierced billets although features of the invention can be embodied in presses for extruding other shapes.

In extruding tubes from hot billets, either solid or of preformed hollow, cylindrical form, Vit is the usual practice to provide an extrusion stem having a bore containing a mandrel. If the billet is a solidbillet, the billet is pierced by the mandrel which is brought into operative relation with the die following' which the extrusion stem is forced against the billet under 'main ram pressure to extrude the billet through the die and around the end of the mandrel thereby to produceta tubular extrusion. If the billet has been preformed vinto a hollow cylindrical form by casting or machining the same into such form, the mandrel does not pierce the billet but merely enters its hollow interior and is then brought into operative relation to the die. This mandrel can berof the oating type or it can be under control of a piston with a stop to accurately place it in proper position with reference to the die. This latter type is particularly useful'for extruding small internal diameter tubing where the mandrel must be ofsmall diameter at the die. With. a positively positioned mandrel it can be necked to have a small diameter at its die end and a large diameterbody, thereby to have the required body size to avoid buckling or breaking under the very high frictional forces imposed on the mandrel. `This latter type of mandrel, that is, the positively positioned mandrel, has only been designed with an external cylinder, that is,`a cylinder arranged externally of the main rram and containing a pistonoperatively connected 'with thermandrel. Since the mandrel is housed within the extrusion stem and since the. extrusion stem is actuated bythe main ram, it will be seen that the use of such an external cylinder for the mandrel poses the problem of a mechanism passing through the extrusion stem, main ram or main cylinder to connectrthe mandrel with the piston in the external cylinder.

It is one of the principal objects of the present invention to provide a mandrel which is positively stopped in its operative position (in contradistinction to a floating mandrel) which is actuated by a piston in an internal cylinder, that is, in a cylinder formed withinthe main ram itself. By such arrangement the problem of providing a mandrel actuating mechanism which must pass through the extrusion stem, main ram or main cylinder is obviated.

Another object is to provide such a positively stopped mandrel actuated by a piston in an internal cylinder in which the positive stop means are very simple, rugged and positive in construction and action. j

Another object is to provide such a positive stop which is readily adjustable to meet all conditions.

At` the end of an extrusion strokea part of the billet cannot be forcedthrough the die and when this part is cut off of the extrusion it forms a discard which must be removed from the press together with a dummy block.

g 2,896,783 Patented `July 28, 1959 It is another object of the invention to provide a mechanism for extending the :effective stroke ofthe main ram and extrusion stem following the shorter extrusion stroke and also following the cutting olf of the discard and which longer effective stroke is operative to eject the discard.

It is another object to provide such a mechanism for extending the effective stroke of the main ramV which is in the form of a simple adjustable stop for limiting the forward movement of the main ram and which in one position permits a longer stroke than in another.

Another object is to provide such an adjustable stop which is adjusted by a rotary movement thereof and in which such rotary movement from one position `to another can be eifected by a simple piston and cylinder.

Another object is to provide such a press which is extremely simple and rugged in construction and not liable to get out of order or require repairs even under conditions of severe and continuous use.

Other objects and advantages of the invention will be apparent from the following description and drawings inwhich: t

Fig. 1 is a simplified and somewhat diagrammatic` horizontal longitudinal section through the axis of extrusion of a tube extruding press embodying the features rof the present invention, parts being eliminated.

Fig. 2 is an enlarged fragmentary view of Ya part of Fig. l and showing the actuating mechanism for the mandrel, as well as the adjustable rotary stop for the movementrof the main ram, in greater detail.

' Fig. 3 is a fragmentary elevtional view, viewed from line 3-3, Fig. 2. Y

Fig. 4 is a fragmentary vertical section .taken on line 4-4, Fig. 2. t

Figs. 5411 are enlarged fragmentary views with parts being eliminated, similarly to Fig. 1 to simplfythe illustration of the invention, and these figures. illustrate the successive steps in producing an extruded tube, in cutting the discard therefrom, and in ejecting this discard from the press. n

The tube extrusion press forming the subject of the present invention is shown as having a fixed platen 15 and a cylinder platen 16 both of whichrare securedyin fixed relation to each other and to the common bed or base (not shown) of the press. The usual main cylinder 19 and fast approach and pullback cylinders 20 are inserted into and xed to the cylinder platen 16. The main ram 21 works in the bore 22 of the main cylinder 19 to which uid is admitted and withdrawn through a passage 23. A large gland or stuffing box 24 and packing 25 are provided in theopen end of the bore 22 around the main ram 21. i

The forward end of the main ram 21 is connected by a large split coupling ring 26 with'the main movable cross head 27 to which the rods 28 of the fast approach and pullback pistons 29 in the fast approach and pullback cylinders 20 lare connected. This cross head is provided With a large bore 30 which opens against the main ram 21 and is also provided with a small through bore 31 in communicating coaxial relation to the large bore 30 and the main ram 21 and slidingly supports a mandrel actuating rod v32. This actuating rod is coupled with a piston or ram 33 iitted in an internal cylinder or bore 34 provided in the main ram 21. Fluid for actuating the piston 33 is supplied to and relieved from the cylinder 34 through a passage 35. The connection between the piston 33 and the mandrel actuating rod 32 is shown as eifected through an internally land externally threaded cylindrical coupling member 36 screwed'into a threaded bore 37 in the piston or ram 33 and having an enlarged threaded end 38 of the mandrel actuating rod 32 screwed into its internally threaded `bore 39; An

.panying claims.

externally threaded lock ring 40 preferably locks this coupling member 36 in position, this lock ring being screwed into a stop collar hereinafter described.

An annular backup block 41 is set into a recess 42 in the end of the main cross head 27 opposing the iixed platen 15, this backup block being provided with a large bore through which the mandrel actuating rod 32 extends. This annular backup block is held in position by extrusion stem 51. This tubular extrusion stem 51 has Y an axial through bore 52 in register with the central bore 43 through the backup block 41 and Vin this bore 52 is arranged the mandrel 53. One end of this mandrel 53 is provided with ya threaded stem 54 which is screwed into la threaded bore in the end of the mandrel actuating rod 32 and the other end of this mandrel is of reduced cylindrical form, as indicated at 55, this reduced cylindrical end 55 of the mandrel determining the internal diameter of the tube produced by the extrusion press and it being a feature of the present invention that this reduced end 55 of the mandrel be positively held in predetermined relation to the die which forms the exterior of the tube being extruded. A dummy block 56 is shown as secured to the free end of the extrusion stem 51.

A feature of lthe present invention resides in the provision of a plurality of stop pins 58 to x the position of the reduced end 55 of the mandrel 53 with reference to the extrusion die. Each of these stop pins 58 has a head 59 at one end and which heads bear against an annular peripheral recess 60 at one end of a stop collar or head 61. The heads 59 of the stop pins 58 are held in abutting relation to the recess 60 by a retaining ring 62 having an annular series of bores or openings through which the stop pins 58 extend and which retaining ring is secured in the annular peripheral recess 60 by radially extending screws 63 as best shown in Fig. 4. The stop pins 58 each extends Ithrough registering bores provided in the main cross head 27, annular backup block 41, and retaining collar 44 and are severally slidingly supported by guide means in the form of bearing bushings 64 carried by the retaining collar 44. The'stop collar 61 is 'screwed on the external threads of the cylindrical coupling member'36 and is held in adjusted relation by a locking nut or screw ring 65. Y

The iixed platen 15 is stationary `and is provided with a horizontal through opening 66 in line with the extrusion stem 51 and through which the extrusion passes. A large rear die backup block 67 is suitably secured to the face of the fixed platen 15 opposing the extrusion stem 51 and is provided with a through opening 68 through which the extrusion passes and which registers with the opening 66 in the fixed platen'15. It will be seen that the fixed platen 15 and the backup block 67 constitutes a composite structure, this composite structure being referred to as the die platen in the accomliner has a cylindrical bore 74 of the same diameter as the extrusion stem 51 with which it alines and which is adapted to receive the billet 75 (Figs. 1 and 5) as well as thedummyblock 56.- A bevel 76 is provided around "2,896,783, f @m Y- the bore 74 of the liner at that end adjacent the die platen 15. The parts 70-73 constitute a billet container structure.

Into this bevel 76 is fitted the beveled end of an annular die 78 which, together with a small backup block 79 and larger backup block 80 for the die, lare mounted in the outer end of a swinging arm 81. This swinging -arm 81 is pivoted to the fixed platen 15 at 82 to swing about an axis in parallel, eccentric relation to the -axis of extrusion so that the die 75, together with its backup blocks 79 and 80, can be swung into and out of operative coaxial relation to the extrusion stem, the die being readily removable from this swinging arm to permit replacement of the die, after each extrusion, witha cooled and lubricated fresh die. The detailed construction of the die, its backup blocks and their mounting on the swinging arm form no part of the present invention,

v reference being made to the copending application of Thweatt and Swanson, Serial No. 242,382, iled August 17, 1951, now Patent No. 2,728,453, issued December 27, 1955, for Extrusion Press for a detailed disclosure of this part of the present extrusion press. Y

Also as disclosed in detail in said Thweatt and Swanson patent, la rotary power driven saw 83 is mounted on a swinging arm 84 to saw the discard from the extruded tube.

To permit the ejection of the discard and dummy block 56 from the container liner 73, means are provided for increasing the effective length of thestroke of the extrusion stem 51 at that stage in the sequence of operations when the discard and dummy block are to be so ejected. This is effected through a rotary stop which A is preferably constructed as follows:

The large retaining collar 44 is provided with a cylindrical neck of reduced diameter projecting toward the die platen 15, 67 and carrying a bearing sleeve 85. On this bearing sleeveis rotatably mounted a castellated ring or collar 86 having an annular series of uniformly spaced and shaped castellations, jaws or protuberances 88 projecting axially toward the die platen 15, 67. These protuberances or jaws can haveface wear plates 87 vand each of which plates can be removably secured by a pair of screws 89.

VThe castellated ring 86 is designed to be rotated by a predetermined number of degrees, from one position to a second position. To this end the castellated ring 86 is provided with a radially extending lug 90 (Fig. 3) and -this lug is arranged to move between two arms 91, Y92 of a stationary C-shaped projection 93 which-is shown as being part of a ring 94 and which ring Ycan be Iixed to the large retaining collar 44 in any suitable manner. Thisring 94 is not shown in Figs. l and 5-11 in order to simplify the illustration of the invention. The arm 91 carries an adjusting screw 95 and the arm 92 carries an adjusting screw 96, the opposing ends of these adjusting screws engaging the lug so that by adjusting these screws the degree of permitted movement as well as the position of the arc'of such movement can be adjusted. The castellated ring 86A is retained in position by a plurality of removable lugs 97 attached-to the end of the large collar 44.

Such movement can be eifected by a piston (Fig. 3) contained in a cylinder 98 and actuating a piston rod 99, vthe cylinder being pivoted, as at 100, to the cross'head 27. The piston rod 99 connects with one arm of a bell crank lever101 pivoted as at 102 tothe main Vcross head 27. The other arm of this `bell crank lever is connected by a link 103 with a lug 107 or the like projecting from the castellated ring 86. In one rotary position of the castellated ring 86, as determined by the piston rod 99 and, say, stop 95, the castellations', jaws or protuberances 88 are in register with correspondingly shaped 'and spaced recesses or pockets 104 in the billet container 71. In the other rotary positionY of the castellated ring 86, as determined bythe piston rod 99 and',

sy, stop 9,6, the castellations, jaws or protuberances 88 are in .register with the opposing face 105 of the container 71. It will be seen that in said one position the main cross head 27 and hence the main ram 21 and extrusion stem 51 have a longer stroke than in said other position because the pockets or recesses 104 receive the castellations, jaws or protuberances to permit such longer stroke.

The arm 81 which carries the die 78 also carries a receiver 106 having an open'side adapted to be brought into line with the extrusion axis to receive the severed discard from the extrusion and the dummy block 56 as hereinafter described. Y

Operation tion where the used die is, discharged `and then to a position where heA can conveniently place a fresh die in the swinging arm.

Atthe time of so loading the die 78 in the swinging arm, the billet container holder 70 had been retracted toward the cylinder platen 16. With the billet container holder 70 s o retracted, the operator then swings the swinging arm 81 to the position shown in Fig. 1 in-which position the die 78 is in axial alinement with the bore of `the liner 73 of the billet container 71.

Contemporaneously with so loading the die 78, a hot billet 75 isl also brought in line with the bore 74 of the liner 73 as shown in Fig. 1 by a billet loader (not shown) which also insertsthe billet 75 in the bore 74 of the container liner 73. At this time the dummy block 56 is alsoV arranged in line with the vbillet tol also be inserted in the bore 74 in rear of the billet. The dummy block 56 is, then pushed into the bore 74 by the forward movement of the Yextrusion stem 51 by the main ram 21. This forward vmovementv of the main ram 21 and extrusion stern 51*r is effectedthrough introduction of fluid pressure in the main cylinder 19 through the passage 23, and while the extrusion .stem 51 is so moving forwardly to push the billet 75 and dummy block 56 into the bore 74, the billet container holder 70 is also being moved towardl the xed ,platen 15' until the front bevel 76 of its linerV 73 is firmly engaged with the bevel of the die 78. This position of the parts isillustrated in Fig. 5. At this time the reduced end 55 of the mandrel 53 is flush with the end of the dummy block 56.

At this time fluid is'introduced through the passage 35 into the cylinder 34 and at the same time uid is relieved through the passage Z3 from the main cylinder 22. The former drives the internal piston or ram 33 toward the xed platen 15 thereby, through the screw coupling member 36 and mandrel actuating rod 32, Iforcing the mandrel 53Y to pierce theY 4billet 75. This piercing removesa core piece 75a from the billet which becomes @Pierced or tubular billet designated at 751:, Fig. 6. A part ofthe core of the billet 75 is also displaced radially outwardly and by backing up the main ram 21 and extrusion stem 51 during this piercing operation, reverse extrusion takes place, that is, the 'billet is elongatedtoward theV cylinder platen 16. This position of the parts is illustrated Yin Fig. 6.

An important feature of the invention is that during this operation culminating in the position shown in Fig. 6, the mandrel 53 is positively positioned with its reduced end 55 in position with reference to the die 78 to produce the required tube. This positioning is effected by engagement of the stop pins 58 with the face 105 of the billet container 71 as shown in Fig. 6. This engagement positively stops further movement of the stop coller 61 to *thelleft as viewedV in Figs. 2 and 6 since this stop collar'is positively Vconnected to the mandrel 53 through the screw coupling 36 and mandrel actuating rod 32, the movement of this mandrel is positively stopped and the reduced end 55 of the mandrel held in fixed relation to the die 78. It will be noted that this positive positioning of the mandrell is effected by the use of the cylinder 34 arranged internally of the main ram 21 and by the simple expedient of the stop pins 58.

Following this, full pressure is introduced through the passage 23 into the `main cylinder 19 to drive the ram 21, main cross head Z7, backup block 41, and extrusion stem 51 forwardly. This extrusion stem 51 moves forwardly in the liner 73 and presses against the dummy block 56 at the rear of the pierced billet 75b so as to force the forward end of the billet between the opening in the die 78 and the reduced end 55 of the mandrel 53. This forms the tubular extrusion 75C. The jaws, castellations or protuberances engage the face 105 of the billet container 71 these parts forming xed stops opposing further movement ofthe main ram 21 so that a discard 75d is left attached to the extrusion 75o. This position of the parts is illustrated in Fig. 7. The billet container holder 70 is 4then moved to the `right 4as viewed in Figs. l and 7 a. short distance' so as to bring the billet container 71 to the position shown in Fig. 8 `and at the same time fluid under pressure is introduced into the left hand ends of the cylinders 20 as viewed in Fig. 1 to move, through the pistons 29, piston rods 28 and cross head 2.7, the ram 21, mandrel 53 and extrusion stem 51 to the position shown in Fig. 8 in which the billet container assembly is separated from the die assembly, the extrusion 75C and its attached discard 75d beingdrawn rearwardly so that the discard can be sawed fromfthe extrusion. This is done by swinging the arm- 84 carrying the rotary power saw 83 between the die 78 and liner 73 so as to sever the discard 75d from the tubular extrusion 75c-as shown in Fig. 8.

The saw 83 isY then withdrawn and the container carrier and its container 71and liner 73 moved to the left as Viewed in Figs. l and 8, the severed discard d thereupon reeugaging the tubular extrusion 75C and giving it a push to initiate its longitudinal discharge from the press.

The container carrier 70 and its container 71 and liner 73 are then moved to the right and the arm 81 is swung so as 4to remove the die 78 from alinement with the ex-` trusion axis of the press and to bring the receiver 106 into -alinement with this axis. At the same time fluid is ad,- mitted to the srnall cylinder 98 (Fig. 3) to rotate, through the bell crank 101 and link 103, the castellated ring 86 so as to bring its jaws, protuberances or castellations 8 8 into alinement with the mating recesses 104 in .the containerV 7.1. This position of the parts is illustrated in Fig. 10. l

Pressure` isznow applied through the passage 23 to the main cylinder 19, to move the main ram 21 to the left as viewedv in Fig. 1-. This moves the main cross head 2.7, backup block 41, extrusion stem 51 and castellated ring 86 towardthe die platen 15, 67. Since the castellations 88 now aline with` the recesses 10-4, the main ram now has a longer stroke, the lengthof the stroke being increased by the depth of the castellations 88 which now enter the recesses 104. This gives the necessary increase in ejective length to the extrusion stem 51 to push the discard 75d and dummy block 56 into the receiver 106 as shown y in Fig. 11.

A fresh die 78 is then inserted in the arm 81 and the parts are returned to the position shown in Fig. 1 and -the castellated ring 86 is indexed back to its original position by the piston in the cylinder 98. The operating cycle as above described can then be repeated.

On the matter of adjusting the apparatus, it will be seen that by loosening the lock ring 40 (Fig. 2) the enlarged threaded end 38 of the mandrel actuating rod 32 can be screwed inV or out to adjust theY effective length of `the-mandrel 53. The lock ring'f40 can then be retightened. This adjustment permits of adjusting lthe eiective length of themandrel 53 to substantially exactly equal the combined length of the extrusion stem 51 and dummy block 56 so that the reduced endV 55 is ush with the far end of the dummy block 56 before the extrusion starts.

To adjust the elective length of the stop pins 58 and hence to locate the reduced end 55 ofthe mandrel 53 in proper relation to the die duringthe extrusion, the radial screws 63 (Fig. 2) can be loosened; the locking ,ring 65 released and the large stop collar 61 turned until it is adjusted longitudinally along the vscrew coupling 36 to provide the desired effective length of the stop pins 58. 'j While the apparatus has been described' as operating upon solid hot billets 75 which are pierced by the mandrel 53 as `shown in Fig. 6, it will be apparent that the apparatus could be used in conjunction with so-called hollow billets, that is, billets which have been cast or machined into cylindrical form so that the necked end of the mandrel 53 merely enters the hollow billet and is then positively positioned with reference to the die 78 as above described.

From the foregoing it will be seen tthatrthe'present invention accomplishes the objectives enumerated, particularly in holding the mandrel in fixed position to the die without requiring a cylinder external to the main ram and in providing a simple rotary stop to increase the elective length of the extrusion stem in ejectng the discard and dummy block.

I claim:

1. In a press for extruding metal shapes, a die platen adapted to carry a die forming the exterior of said shapes, a cylinder platen carrying a main cylinder housing a main ram structure projectable toward and from said die platen, an extrusion stem projecting from said main ram structure tofward said die, a billet container structure having a through bore in line with said die and extrusion stem and movably mounted between said main ram strueture and die for movement parallel with said extrusion stern; the combination therewith of means for ejecting the severed discard and any dummy block from said through bore following the forming of the extrusion, and severing the end of the extrusion at which the discard is formed, comprising a ring rotatably mounted on one of said structures on an axis generally parallel with the movement of said ram structure, a protuberance on said ring projecting toward the other of said structures, said other of said structures being provided with a recess to receive said protuberance, and means arranged to rotate said ring to bring it into and out of register with said recess.

2. A press as set forth in claim lwherein said ring is in the fonn of a castellated ring with each castellation thereof forming said protuberance.

3. A press as set forth in claim 2 wherein said castellated ring is provided with a lug and wherein said one of said structures is provided with a pair of opposed adjustable stops limiting the arcuate movement of said lug.

4.` A press las set forth in claim 3 wherein a piston and cylinder rotates said castellated ring, one being connected with said castellated ring and the other connected with saidtone of said structures.

5; In an extrusion press for extruding metal tubes, a die platen adapted to carry a die forming the exterior of said tubes, a cylinder platen carrying a main cylinder, a main ram in said main cylinder projectable toward said die platen and havinga generally concentric cylinder *pro-i vided with an end head opposing said die platen, fa tubular extrusionfs'tem projecting Vconcentrically from -said vend head and having a longitudinal through bore in line with a borethroughsaid/end head, a billet container structure having a through bore in line 'with said die and tubular extrusion stern and movably mounted between said main ram and die for movement parallel with said tubular extrusion stem, a piston arranged in said generally concentric cylinder and having an internally threaded boreopening toward said end head, a mandrel slidingly ttiug in said'tubular extrusion stem, a mandrel holder having 'a threaded end adjustably screwedinto said threaded bore and having its opposite end connected with the said mandrel, the youter end of said mandrel being of ,reduced size to coact with said die in producing the desired cross sectional form orf said tubes, a plurality of pins fixed to project from said piston through bores in said end head toward said billet container structure, the ends of said pins engaging said billet container structure when said end of a reduced size of said mandrel comes intov predetermined closely spaced relation tosaid die thereby to position said end of reduced size of 'said mandrel in a definite relation to said die as said tube is extruded.

6. In an extrusion press for extruding metal tubes, aV v die platen adapted to carry a die forming the exterior of said tubes, a cylinder platen carrying a main cylinder, a mainram in said main cylinder projectable toward said die platen and having a generallyl lconcentric cylinder provided with an end head opposing said die platen, a ,tubular extrusion stem projecting concentrically fromsaid end head and having a longitudinal through bore in line with a bore through said end heada billet container structure having a through bore in line with said die'and tubular extrusion stem and movably mounted between said main ram and die for movement parallel with said tubular extiusion stem, a piston arranged in -said `generally'concentric cylinder and havingra coaxially externally threaded couplingY member projecting toward said end head, a mandrel projecting from saidpiston and slidingly ittin'g in said tubular extrusion stem and in said bore through said end head, the outer end of saidmandrel'bein'g of reduced size to coact with said die in producing therdesired cross-sectional form of said Vtubesfan internally threaded collar screwed lon said coupling member, a plurality of pins xed to'project frmsaid collar through bores in said end head toward said billet container structure, the ends of said pins engaging'isaid billet container stuucture when said end of:v a reduced size of said mandrel comes into predetermined closely spaced relation Yof said die thereby to position .said end ,pcf reducedjsize ,of said mandrel in a definite relation to said die assaidtube is extruded. e Y

References Citedin the tile of this patent. l

UNITED STATES PATENTS 1,084,881 Gamen f Jan.. 20,1914 2,142,704 'Sparks' f.. ..-Ian. 3, 1939 2,385,144 Lomi sept. 18,1945 2,728,453 Thweatt et al. Dec. 27,1955 2,732,066 Aibers t 11an. 24,1956 2,751 076 Lombard June 19, 1956 i l FOREIGN PATENTS j 516,511 Belgium 1.` Jan. 15, V1953 629,573

Great Britain ..j j ....V Sept. ,22, 1949 

